In one type of acoustic reproduction device, such as an open fitting hearing aid, a vent connecting the inside of the external ear canal to the outside is provided to alleviate an occlusion effect when wearing the hearing aid (for example, see JP 2006-304147 A (PTL 1)). FIG. 10 schematically illustrates one type of hearing aid 90. This hearing aid 90 includes a microphone 91, an earphone 92, and a vent 93. The microphone 91 collects sound from a sound source, and the earphone 92 causes the user to hear the sound collected by the microphone 91. The vent 93 is a hole connecting the inside of the external ear canal to the outside, as described above. As a result of the vent 93, the external ear canal is not completely sealed. Therefore, the occlusion effect that occurs when wearing the hearing aid 90 is alleviated.